1. Field of the Invention
The present invention relates to a pressure sensor.
2. Description of Related Art
Patent Document 1 recites a configuration of a pressure sensor. According to the configuration, the pressure sensor includes an IC chip, a wire bonding element, an adhesive member, and a case having an air introduction passage. The air introduction passage has a pectinated or helical shape. The adhesive element is disposed in the air introduction passage. The adhesive element protects the IC chip and the wire bonding element from a small insect in such a manner that, when a small insect enters the pressure sensor, the insect may be stuck in the adhesive element.
Patent Document 2 recites another configuration of a pressure sensor. According to the configuration, a filter is disposed at an open end of an air passage to effectively inhabit a foreign substance from entering the air passage.
Patent Document 3 recites another configuration. According to the configuration, a radius of an air passage is enlarged at an open end of an air passage to prevent an insect from building a nest at an inner wall of the open end of the air passage.
Patent Document 1: JP-A-2006-105853
Patent Document 2: JP-A-H9-43085, corresponding to U.S. Pat. No. 5,900,554
Patent Document 3: JP-A-H11-101659
According to Patent Document 1, however, since the air introduction passage has a pectinated shape or a helical shape, and since the adhesive element is disposed in the air introduction passage, the pressure sensor eventually has a complex configuration. In addition, when an insect worms on the side wall to enter the sensor, the insect may be eventually stuck in the air introduction passage. Stuck insects may get jammed in the air introduction passage and may become a bottleneck for air introduction. It becomes therefore difficult for the pressure sensor to detect air pressure with high accuracy.
According to Patent Document 2, since the pressure sensor requires a filter as an additional part, the number of parts and manufacturing cost increase. Also, when a filer is clogged, the clogged filter becomes a bottleneck for air introduction in a similar manner to that in the above case, and it becomes difficult for the pressure sensor to detect air pressure with high accuracy.
According to the Patent Document 3, the enlarged radius of the open end of the air passage can prevent an insect from building a nest but not prevent an insect from entering.